Iron cross 1st class by Wilhelm Deumer, Lüdenscheid. Three part construction with magnetic, iron core. Maker marked with the LDO code of Deumer "L/11" on the pin. Excellent condition with almost the entire frosting on the frame and an almost perfect black core. The cross comes in its original case of issue. 
Deumer "L/11" marked crosses are common, but the marking is almost always below the catch. The crosses with maker marking on the pin are truly rare.
Very rare cross in excellent to mint condition!